Continuous coiled sucker rod has been used in oil wells for the last 32 years. It is assembled in manufacturing plants from a number of pieces of steel rod supplied by a steel mill using a flash-butt welding machine. This is the most effective and reliable method of joining coiled sucker rod.
During installation of a coiled sucker rod and servicing of wells with a coiled sucker rod the need for joining two pieces of a coiled sucker rod quite often arises. Several methods of joining the continuous coiled sucker rod in the field were considered and experimented with (such as mechanical joints or explosive welding and hand welding with portable electrical welding machines etc.) and found impractical.
At present time the only reliable and practical method of joining a continuous coiled sucker rod in the field is electrical flash-butt welding with a truck or a trailer mounted flash-butt welder; all field-joining of coiled sucker rod is done using this method. This is a very much the same method as the one used in a manufacturing plant. The biggest drawback of this method is its huge requirement of electric power, which has to be supplied from many large, heavy, and expensive batteries. These batteries need to be recharged very often and their life is limited.